1. Field of the Invention
Embodiments of the present invention generally relate to an integrated conductor/suspension structure for supporting and electrically connecting a write/read head in a hard disk drive.
2. Description of the Related Art
Hard disk drives typically include a rotating rigid magnetic storage disk and an actuator for positioning a head slider at different radial locations relative to the axis of rotation of the disk, thereby defining numerous concentric data storage tracks on each recording surface of the disk. Although numerous actuator structures are known in the art, in-line rotary voice coil actuators are now most frequently employed due to their simplicity, high performance, and their ability to be mass balanced about their axis of rotation, the latter being important for making the actuator less sensitive to perturbations. A closed-loop servo system within the disk drive is conventionally employed to operate the voice coil actuator and thereby position the heads with respect to the disk surface.
An air bearing surface on a head slider supports the head slider at a small distance away from the surface of the magnetic disk. The head slider also includes a write/read head for writing and reading data to and from the magnetic disk. The write/read head is connected by electrical wires or conductors to associated drive electronics, e.g., a proximately located preamplifier chip and downstream read channel circuitry typically carried on a circuit board (along with other circuitry) that is attached to the head/disk assembly. Single write/read head designs typically require two wire connections while dual designs having separate reader and writer elements require four wire connections. Magnetoresistive (MR) heads in particular generally require four wires. Head sliders are generally mounted to a gimbaled flexure structure attached to the distal end of a suspension's load beam structure, which in turn is connected to the actuator. A spring biases the load beam and the head slider towards the disk, while the air pressure beneath the head slider pushes the head slider away from the disk. An equilibrium distance defines an “air bearing” and determines the “flying height” of the head slider.
The disk drive industry has been progressively decreasing the size and mass of the head slider structures in order to reduce the moving mass of the actuator assembly and to permit closer operation of the transducer to the disk surface, the former giving rise to improved seek performance and the latter giving rise to improved transducer efficiency that can then be traded for higher areal density. Smaller slider structures generally require more compliant gimbals, hence the intrinsic stiffness of the conductor wires attached to the head slider can give rise to a significant undesired bias effect. To reduce the effects of this intrinsic wire stiffness or bias, integrated suspension/conductor structures have been proposed which include hybrid stainless steel flexure and conductor structures. Such hybrid designs typically employ stainless steel flexures having deposited insulating and conductive trace layers for electrical interconnection of the head to the associated drive electronics.
These hybrid flexure designs employ relatively lengthy runs of conductor trace pairs or four-wire sets which extend from bonding pads at the distal, head-mounting end of the flexure to the proximal end of the flexure. Theses traces provide a conductive path from the read/write head along the length of the associated suspension structure to the preamplifier or read-channel chip(s). Because the conductor traces are positioned extremely close to, but electrically isolated from, the conductive stainless steel flexure structure which is in turn grounded to the load beam, and because of the relatively high signal rates being transferred, the conductor trace inductance and mutual coupling, as well as conductor trace resistance and trace capacitance to ground, can give rise to unwanted signal losses, reflections, distortion, and inefficient signal/power transfer. The unwanted signal losses and reflections tend to deleteriously affect the performance of the read/write head, interconnect structure, and driver/preamplifier circuit.